The invention relates to the art of perfumery, and particularly to methods for employing fragrances.
Fragrances are marketed in a variety of forms, the most common form being a solution of essential oils in ethyl alcohol. The characteristic scent of a particular fragrance is determined by the balance of its unique mixture of essential oils. Essential oils comprise organic compounds having a pleasant scent, and designated, in broad terms, according to their volatility, as top notes (most volatile), middle notes (intermediate volatility), and base notes or fixatives (low volatility).
Fragrances are manufactured in varying concentrations of essential oils in alcohol and other organic solvents, designated in increasing order of concentration as eau de toilette, after shave, or toilet water, 2-5%; eau de cologne or cologne, 5-10%; eau de parfum or eau de perfume, 11-15%; and parfum or perfume 16-50%. Users perceive perfume to be richer, more full-bodied than a less concentrated cologne, and when applied to skin, perfume emits a stronger, more persistent scent. Typically, the price of perfume is 3-10 times that of eau de perfume, 10-15 times that of cologne, and 15-20 times that of eau de toilette. A manufacturer usually markets a perfume and a lower priced cologne version of the same fragrance. Both have the same overall fragrance character, but the perfume version will contain more expensive, more complex essential oils, including more fixatives.
Fixatives have an important role in the complex art of perfumery. The earliest known fixatives were natural musks, such as that obtained from the musk deer. Crude extracts from the musk deer and civet cat were prized historically as ingredients indispensable to the manufacture of fine fragrances. The chemical isolation and characterization of the active compounds of the animal musks, muskone and civetone, indicated that these materials were macrocyclic compounds, having seven or more carbon atoms in a ring. Musk from the ox was found to be methyl-substituted-cyclopentadecanone, and that of the civet cat unsaturated cycloheptadecanone. Similar musk-like substances were later found in angelica root oil and ambrette seed. These natural musks of vegetable origin were found to be macrocyclic lactones. Angelica root oil contains cyclopentadecanolactone and ambrette seed oil contains ambrettolide, 7-cyclohexadecanolactone. Early chemists believed that in vitro synthesis of such compounds would be exceedingly difficult because of the instability of the ring structures. Accordingly, natural musks of both animal and vegetable origin commanded a high price.
However, in 1888 the chemist Baur found that a nitrobenzene compound, 2,4,6-trinitro-3-methyl-tert-butylbenzene possessed a strong musk odor, and several nitrobenzene compounds having a musk character were subsequently synthesized. Musk perfumes were also found in synthetic compounds having other chemical structures, such as steroid (16-androsten-3-ol), indane, benzene, and tetralin types (Berends, W. American Perfumer and Cosmetics 80:35-38 (1965)). Chemists also discovered that large macrocyclic structures are not inherently unstable, because valence bond angles can be maintained if the ring assumes a non-planar configuration, and synthetic fixatives of this class were made. Thus several classes of synthetic compounds useful as fixatives became available and these were also designated musks, by derivation and analogy to the original animal extract.
A structure-odor relationship among fixative compounds has not been fully determined. It is suggested that the common characteristics of useful compounds are that they have (1) a molecular weight of 200-300; (2) a compact molecular structure; and (3) a functional group. This broad definition accommodates several chemical classes.
The most important class of musks are macrocyclic compounds, having from: 15-20 ring atoms and at least one functional group. Among this group there are at least five types: lactones, ketones, carbonates, anhydrides, and cyclic oxides, sulfides and amines. Another class is that of the nitro musks. Of all the nitro musks synthesized since Baur, only five are in commercial use today: Musk Xylene, Musk Ambrette, Musk Tibetene.TM., Musk Ketone, and Moskene.TM. (Givauden Corp., Delawanna, New Jersey). All comprise a benzene structure substituted with 2-3 NO.sub.2 groups, 1-3 CH.sub.3 groups, and a tert-butyl group (Carpenter, M. and Easter, W. J. Organic Chemistry 19:77,87 (1954). A third class is that of the hydroaromatic polycyclics, comprising the indane type having the basic structure (I); the steroid type, having the basic structure (II); and the tetralin type, having the basic structure (III). Yet another class is that of the oxahydroaromatics, having a basic structure such as (IV). ##STR1##
Although the musk-like fixative compounds have a wide range of pleasant odors, they are used in perfumery not particularly for this property, but for their ability to impart a refinement to luxury perfumes which is subjective and therefore difficult to define. This contribution has been expressed, however as "fixation," "exaltation," "rounding," or "cachet," as well as "noble," and "luxurious."
It would be desirable to enjoy these characteristics ordinarily found only in fragrances of the expensive luxury perfumes while using less costly products. It would also be desirable to have a product which would convert any fragrance into its perfume counterpart. Accordingly it is an object of the invention to provide a method to enhance the properties of colognes and other lower priced fragrance preparations having lower concentrations of essential oils to make them comparable to perfumes at a cost savings to the consumer.